Prevalence of temporomandibular disorders among Palestinian medical students

Temporomandibular joint disorder (TMD) is a collective term that involves alterations in the temporomandibular joint, muscles of mastication and the occlusion. The TMD disorder is a common health problem which affects about 33% of the population within their lifetime. The aim of this study was to evaluate the prevalence of TMDs among university students in Palestine. The role of various risk factors in the etiology of TMD symptoms was also addressed. This is a cross sectional study based on a self-administered questionnaire. The study sample consisted of 416 dental and medical field students from all cities of Palestine studying at Arab American University of Palestine (with an age range of 18 – 27 years). In this study, 63.5% (n = 264) of the investigated students had at least one TMD symptom; clenching was the most prevalent TMD (35.6%) followed by joint noise (33.4%) while locked jaw was the least prevalent (10.6%) symptom. In the conclusion high prevalence of TMD among Palestinian medical students was reported, females reported more pain on TMJ area than males, age group (23 to 25) years reported more frequency of clenching than the other age groups, and strong correlation was found between stress, headache and TMD. Keywords: Temporomandibular Disorder; Clenching; Stress; Headache 1. Introduction There is no doubt that temporomandibular Disorder (TMD) is a collective term that comprises alterations in the temporomandibular joint (TMJ), muscles of mastication and the occlusion. [1] The TMD disorder is a common health problem which affects about 33% of the population within their lifetime. [2] Epidemiologic studies show that TMD symptoms are most prevalent among patients between fifteen and twenty-five years of age; symptoms then level out as patients approach age thirty five. [3] The prevalence of TMD varies according to the population; Macfarlane et al. (2002) reported a 26% overall prevalence of Oro-Facial Pain disorder among English people, [4]. Pow et al. [5] reported jaw pain among 33% of the Chinese people in Hong Kong. Due to its high prevalence, TMD became an important issue in the medical field. Patients with TMD usually suffer from joint pain, limited jaw movement, joint sounds and frequent headaches. History of facial trauma, bruxism, sleep problems, pain elsewhere in the body, and high levels of psychological distress have been linked with TMD development. [6-8] Although the orthodontic community has become increasingly interested in TMD, there are no previous studies that were conducted in Palestine in order to evaluate the prevalence of TMD, accordingly this study aimed to evaluate the prevalence of TMD and the associated risk factors among university students. Jaradat et al. / World Journal of Advanced Research and Reviews, 2020, 06(01), 146–152 147 2. Subjects and methods This is a cross sectional study based on a self-administered questionnaire. A total of 416 students (122 males and 294 females) from all cities of Pleatine studying at the faculties of dentistry and Allied Medical Sciences/ Arab American University of Palestine (Mean age 21.2 ± 1.8 years with a range of 18 – 27 years) were invited to fill the questionnaire. The students were divided into four main age groups as shown in Table 1. Table 1 Age distribution of the study sample Age Number (%) Mean 18 to < 21 years 151 (36.3) 19.3 ± 0.7 21 to < 23 years 168 (40.4) 21.6 ± 0.5 23 to < 25 years 81 (19.5) 23.2 ± 0.4 25 to < 28 years 16 (3.8) 25.6 ± 0.7 Total 416 (100) 21.2 ± 1.8 The used questionnaire was based on the guidelines recommended by the American Dental Association [9]. It consisted of 11 questions (Table 2) with main two components; the first five questions were related to TMD symptoms and the last six questions were related to risk factors that might be associated with TMD. Table 2 The questionnaire contents Question Response Yes No Are you aware of noise in the jaw joints? Do you have limitation in mouth opening? Do you have pain in or about the ears, temples, or cheek area? If yes, which side? Has your mouth ever been locked open so you were not able to close it? If yes, how many times? Do you have difficulty and / or pain, while chewing or talking? Have you ever had trauma to the head and neck area? Where and when? Do you have frequent headaches? Do you have stress, or being under stressful circumstances? Are you aware of clenching of your teeth? Do you have pain in other body joints? Have you previously been treated for a jaw joint problem? If yes, when? 3. Statistical analysis Statistical analysis was performed using IBM SPSS (SPSS Version 23, IBM©, Armonk, NY, USA). Frequencies and percentages were calculated. Pearson Chi2 test was used to study the association between TMD symptoms, gender, age and risk factors. Differences at the 5% level were accepted as being statistically significant. Jaradat et al. / World Journal of Advanced Research and Reviews, 2020, 06(01), 146–152 148 4. Results TMD symptoms showed a high prevalence among the investigated university students. Sixty-three and half percent (264 students) of the total sample reported at least one TMD symptom; the rest (36.5%, 152/416) did not report any symptom. Only 0.5% (2/416) of the total sample reported all investigated symptoms. The distribution of TMD symptoms in the studied sample is shown in Figure 1. Figure 1 The distribution of students according to the number of symptoms they exhibited The most prevalent TMD symptom reported was clenching (35.6%) followed by TMJ noise (33.4%). Locked jaw was the least reported (10.6%) symptom. The prevalence of each symptom is shown in Figure 2. Figure 2 Prevalence of TMD symptoms in the total sample Almost one quarter of the students (27.3%, n = 72) who reported at least one TMD symptom were males while the rest were females (72.7%, n = 192). There was no significant difference in the reported TMD symptoms between males and females except for pain on TMJ area; more females reported pain on TMJ area (P = 0.012). Most of the affected subjects were within the first and second age groups. Table 3 shows the prevalence of each symptom according to gender and age groups. Jaradat et al. / World Journal of Advanced Research and Reviews, 2020, 06(01), 146–152 149 Table 3 Prevalence of TMD symptoms according to age and gender Gender Statistic Age Group Total Age Grp 1 (151 students) Age Grp 2 (168 students) Age Grp 3 (81 students) Age Grp 4 (16 students) Males Number of male students with TMD symptoms 25 23 20 4 72 % within Gender 34.7% 31.9% 27.8% 5.6% 100.0% % Total sample 9.5% 8.7% 7.6% 1.5% 27.3% Females Number of female students with TMD symptoms 67 80 41 4 192 % within Gender 34.9% 41.7% 21.4% 2.1% 100.0% % of Total sample 25.4% 30.3% 15.5% 1.5% 72.7% Total 92 103 61 8 264 There was no significant gender difference in the occurrence of TMD symptoms except for the symptom pain on temporomandibular joint area which occurred more among females (as shown in Table 4) Table 4 Association between gender and TMD symptoms Symptom Gender P-Value Male (122) Female (294) Number (%) Number (%) Noise 38(31.1) 101(34.4) 0.528 Limited jaw movement 14(11.5) 41(13.9) 0.498 Pain on TMJ area 12(9.8) 59(20.1) 0.012 Locked jaw 16(13.1) 28(9.5) 0.278 Pain on function 17(13.9) 33(11.2) 0.439 Clenching 40 (32.8) 108 (36.7) 0.444 When comparing the prevalence of each symptom within the different age groups, apart from clenching, the results showed no significant difference between the different age groups and all TMD symptoms (Noise, limited jaw movement, pain on TMJ area, locked jaw and pain on function). Students in the third age group had the highest prevalence (p value of 0.000) of clenching compared with the other age groups. The age-wise prevalence distribution is shown in Table 5. Table 5 Age groups associated with Prevalence of TMD symptoms in the studying sample Symptom Age group P-Value Group 1 Group 2 Group 3 Group 4 Number (%) Number (%) Number (%) Number (%) Noise 42(27.8) 56(33.3) 36(44.4) 5(31.3) 0.086 Limited jaw movement 24(15.9) 23(13.7) 8(9.9) 0(0) 0.241 Pain on TMJ area 23(15.2) 30(17.9) 17(21) 1(6.3) 0.451 Locked jaw 12(7.9) 20(11.9) 10(12.3) 2(12.5) 0.626 Pain on function 20(13.2) 17(10.1) 11(13.6) 2(12.5) 0.806 Clenching 38(25.2) 64(38.1) 43(53.1) 3(18.8) 0.000 Regarding causative effect of TMD risk factors on the development of TMD symptoms, the results revealed that previous trauma was significantly associated with increased risk of limited joint movement (p = 0.013). Both headache and stress were statistically associated with all TMD symptoms except joint noise. Jaradat et al. / World Journal of Advanced Research and Reviews, 2020, 06(01), 146–152 150 Artheralgia did significantly increase the risk of pain on temporo-mandibular joint area and clenching. Previous joint treatment was significantly associated with increased pain levels on temporo-mandibular joint area and the development of a locked jaw situation. The associations between TMD symptoms and the associated risk factors are shown in Table 6. Table 6 Risk factors for TMD development Risk factors Symptoms Noise Limited jaw movement Pain on TMJ area Number (%) P Number (%) P Number (%) P Previous trauma Yes 15(30.6) 0.658 12(24.5) 0.013 13(26.5) 0.061 No 124(33.8) 43(11.7) 58(15.8) Headache Yes 65(34.9) 0.551 35(18.8) 0.002 54(29) 0.000 No 74(32.2) 20(8.7) 17(7.4) Stress Yes 91(35.7) 0.216 45(17.6) 0.001 58(22.7) 0.000 No 48(29.8) 10(6.2) 13(8.1) Artheralgia Yes 32(36.8) 0.454 15(17.2) 0.212 21(24.1) 0.049 No 107(32.5) 40(12.2) 50(15.2) Previous treatment Yes 11(50) 0.090 5(22.7) 0.176 10(45.5) 0.000 No 128(32.5) 50(12.7) 61(15.5) Risk factors Symptoms Locked jaw Pain on function Clenching Number (%) P Number (%) P Number (%) P Previous trauma Yes 7(14.3) 0.369 7(14.3) 0.603 19(38.8) 0.619 No 37(10.1) 43(11.7) 129(35.1) Headache Yes 33(17.7) 0.000 33(17.7) 0.001 85(45.7) 0.000 No 11(4.8) 17(7.4) 63(27.4) Stress Yes 39(15.3) 0.000 42(16.5) 0.000 119(46.7) 0.000 No 5(3.1) 8(5) 29(18) Artheralgia Yes 11(12.6) 0.481 15(17.2) 0.092 39(44.8) 0.043 No 33(10) 35(10.6) 109(33.1) Previous treatment Yes 6(27.3) 0.009 9(40.9) 0.000 9(40.9) 0.591 No 38(9.6) 41(10.4) 139(35.3) 5. Discussion Although TMD is a prevalent disease affecting young adults (Magnusson et al 2000), there is lack in the literature about its prevalence in the Palestinian population. Accordingly, the aim of this study was to study the prevalence of TMD symptoms among a group of university students. Jaradat et al. / World Journal of Advanced Research and Reviews, 2020, 06(01), 146–152 151 In this study, students from the dental and medical fields were chosen to answer the questionnaire because they have more knowledge about the temporomandibular joint problems compared to students from other faculties in the university. The results of this study revealed a high prevalence (63.5%) of TMD symptoms among the investigated students. This result was close to what was found by some other studies. [10,11] Among the investigated TMD symptoms, clenching was the most prevalent among the investigated students with a prevalence of about 35.6% (148/416 students). This result was in agreement with other studies which proved the strong relationship between clenching and the development of TMD. [12] Joint Noises were the second most reported symptom with a prevalence of about 33.4% (139/416 students). Apart from clenching, no significant correlation between different age groups and the reported TMD symptoms (Noise, limited jaw movement, pain on TMJ area, locked jaw and pain on function). Other studies reported similar results. [13] [14] In Most of the studies, females reported higher prevalence of TMD symptoms than males. Contrary to most studies reported in the literature, in this study there was no significant gender difference in the occurrence of TMD symptoms except for the symptom pain on temporomandibular joint area which occurred more among females. [10-11, 16-20] Students in the third age group had the highest prevalence of clenching symptom compared to other groups. This could be explained by the fact that students in the graduation years may suffer high levels of anxiety, stress and headache that may trigger the development of TMD symptoms. This goes in hand with what was found by Gerke et al. (1990) who proved the intimate relationship between psychological and emotional factors and the development of TMD. [15] This study revealed that stress and headache are closely related to the development of TMDs. Headache was the risk factor mostly associated with the TMD development followed by stress. This finding goes in part with what was found by Young (1999) who considered headache as being the most common risk factor associated with TMD development. [21-23] 6. Conclusion Based on the findings of our study, a high prevalence of TMD among Palestinian medical students with female students reporting more pain on TMJ than males.Age group (23 to 25) years reported more frequency of clenching than the other age groups and a strong correlation was found between stress, headache and TMD. Compliance with ethical standards Disclosure of conflict of interest There is no conflict of interest exist among all authors. Statement of informed consent Informed consent was obtained from all individual participants included in the study. References [1] Tatiana V, Macfarlane, Pamela Kenealy H, Anne Kingdon, Bengt O, Mohlin J, Richard Pilley, Steve Richmond, William C. (2009). Shaw.Twenty-year cohort study of health gain from orthodontic treatment: Temporomandibular disorders, 135(6), 692–692. [2] Wright EF and North SL. (2009). Management and treatment of temporomandibular disorders: a clinical perspective. J Man Manip Ther., 17(4), 247-54. [3] Magnusson T, Egermark I and Carlsson GE. (2000). A longitudinal epidemiologic study of signs and symptoms of temporomandibular disorders from 15 to 35 years of age. J Orofac Pain, 14, 310-9. [4] Macfarlane TV, Blinkhorn AS, Davies RM, Kincey J and Worthington HV. (2002). Oro-facial pain in the community: prevalence and associated impact. Community Dent Oral Epidemiol, 30, 52–60. Jaradat et al. / World Journal of Advanced Research and Reviews, 2020, 06(01), 146–152 152 [5] Pow EH et al. (2002). Prevalence of symptoms associated with temporomandibular disorders in Hong Kong Chinese. J Orofac Pain, 15(3), 228-34. [6] Macfarlane TV, Blinkhorn AS, Davies RM and Worthington HV. (2003). Association between local mechanical factors and orofacial pain: survey in the community. J Dent, 31, 535-42. [7] Macfarlane TV and Worthington HV. (2004). Association between orofacial pain and other symptoms: a population-based study. Oral Biosci Med, 1, 45-54. [8] Velly AM, Gornitsky M and Philippe P. (2003). Contributing factors to chronic myofascial pain: a case-control study. Pain, 104, 491-9. [9] Nassif NJ and Hilsen KL. (1992). Screening for temporomandibular disorders: history and clinical examination. American Dental Association. J Prosthodon, 1(1), 42-46. [10] Pedroni CR, Oliveira AS and Guaratini MI. (2003).Prevalence study and symptoms of temporomandibular disorders in university students. J Oral Rehabil, 30(2), 283-9. [11] Muthukrishnan A and Sekar GS. (2015). Prevalence of temporomandibular disorders in Chennai population. J Indian Acad Oral Med Radiol, 27, 508-15. [12] Joelma Magalhães da Costa, Rafael Ribeiro, Tabajara de Oliveira Gonzalez, Cid Andre Fidelis de Paula Gomes, Fabiano Politti and Daniela Aparecida Biasotto-Gonzalez. (2012). Association between temporomandibular disorder and bruxism among children aged 5 to 11 years.Med Sci Tech, 53(1), RA33-36. [13] Gesch D, Bernhardt O, Alte D, Schwahn C, Kocher T, John U and Hensel E. (2004).Prevalence of signs and symptoms of temporomandibular disorders in an urban and rural German population: results of a populationbased Study of Health in Pomerania. Quintessence In, 35(2), 143150.   [14] Soukaina R, Zaid HB, Wala MAC, Faleh S, Osama S and Darwish HB. (2009). Prevalence of Temporomandibular Joint Disorders among Students of the University of Jordan. J Clin Med Res, 1(3), 158-164. [15] Gerke DC, Goss ANand Bassett DL. (1990). Psychological factors in temporomandibular joint dysfunction: life events. Aust Prosthodont J, 4, 29-34. [16] Nomura K, Vitti M, de Oliveira AS, Chaves TC, Semprini M, Siéssere S, Hallak JE and Regalo SC. (2007). Use of the Fonseca’s questionnaire to assess the prevalence and severity of temporomandibular disorders in Brazilian dental undergraduates. Braz Dent J, 18(2), 163-167. [17] De Oliveira AS, Dias EM, Contato RG and Berzin F. (2006). Prevalence study of signs and symptoms of temporomandibular disorder in Brazilian college students. Braz Oral Res, 20(1), 3-7. [18] Bagis B, Ayaz EA, Turgut S, Durkan R and Özcan M. (2012). Gender difference in prevalence of signs and symptoms of temporomandibular joint disorders: a retrospective study on 243 consecutive patients. Int J Med Sci, 9(7), 539-544. [19] Bahrani F, Ghadiri P and Vojdani M. (2012). Comparison of temporomandibular disorders in Iranian dental and nondental students. J Contemp Dent Pract, 13(2), 173-177. [20] Chuang SY. (2002). Incidence of temporomandibular disorders (TMDs) in senior dental students in Taiwan. J Oral Rehabil, 29(12), 1206-1211. [21] Young DM, Mentes JC and Titler MG. (1999). Acute pain management protocol. J Gerontol Nurs. Jun, 25(6), 10-21. [22] Carlo Di Paolo, Anna D’Urso, Piero Papi, Francesco Di Sabato, Daniele Rosella, Giorgio Pompa and Antonella Polimeni. Temporomandibular Disorders and Headache: A Retrospective Analysis of 1198 Patients. Pain research and management [23] Ciancaglini R and Radaelli G. (2001). “The relationship between headache and symptoms of temporomandibular disorder in the general population,” Journal of Dentistry, 29(2), 93– 98. How to cite this article Jaradat MR, Jarbawi MM, Al-Khateeb SN and Rahhal AA. (2020). Prevalence of temporomandibular disorders among Palestinian medical students. World Journal of Advanced Research and Reviews, 6(1), 146-152.


Introduction
There is no doubt that temporomandibular Disorder (TMD) is a collective term that comprises alterations in the temporomandibular joint (TMJ), muscles of mastication and the occlusion. [1] The TMD disorder is a common health problem which affects about 33% of the population within their lifetime. [2] Epidemiologic studies show that TMD symptoms are most prevalent among patients between fifteen and twenty-five years of age; symptoms then level out as patients approach age thirty five. [3] The prevalence of TMD varies according to the population; Macfarlane et al. (2002) reported a 26% overall prevalence of Oro-Facial Pain disorder among English people, [4]. Pow et al. [5] reported jaw pain among 33% of the Chinese people in Hong Kong.
Due to its high prevalence, TMD became an important issue in the medical field. Patients with TMD usually suffer from joint pain, limited jaw movement, joint sounds and frequent headaches. History of facial trauma, bruxism, sleep problems, pain elsewhere in the body, and high levels of psychological distress have been linked with TMD development. [6][7][8] Although the orthodontic community has become increasingly interested in TMD, there are no previous studies that were conducted in Palestine in order to evaluate the prevalence of TMD, accordingly this study aimed to evaluate the prevalence of TMD and the associated risk factors among university students.

Subjects and methods
This is a cross sectional study based on a self-administered questionnaire. A total of 416 students (122 males and 294 females) from all cities of Pleatine studying at the faculties of dentistry and Allied Medical Sciences/ Arab American University of Palestine (Mean age 21.2 ± 1.8 years with a range of 18 -27 years) were invited to fill the questionnaire. The students were divided into four main age groups as shown in Table 1. The used questionnaire was based on the guidelines recommended by the American Dental Association [9]. It consisted of 11 questions (Table 2) with main two components; the first five questions were related to TMD symptoms and the last six questions were related to risk factors that might be associated with TMD. Have you previously been treated for a jaw joint problem? If yes, when?

Statistical analysis
Statistical analysis was performed using IBM SPSS (SPSS Version 23, IBM © , Armonk, NY, USA). Frequencies and percentages were calculated. Pearson Chi 2 test was used to study the association between TMD symptoms, gender, age and risk factors. Differences at the 5% level were accepted as being statistically significant.

Results
TMD symptoms showed a high prevalence among the investigated university students. Sixty-three and half percent (264 students) of the total sample reported at least one TMD symptom; the rest (36.5%, 152/416) did not report any symptom. Only 0.5% (2/416) of the total sample reported all investigated symptoms. The distribution of TMD symptoms in the studied sample is shown in Figure 1.

Figure 1
The distribution of students according to the number of symptoms they exhibited The most prevalent TMD symptom reported was clenching (35.6%) followed by TMJ noise (33.4%). Locked jaw was the least reported (10.6%) symptom. The prevalence of each symptom is shown in Figure 2. Almost one quarter of the students (27.3%, n = 72) who reported at least one TMD symptom were males while the rest were females (72.7%, n = 192). There was no significant difference in the reported TMD symptoms between males and females except for pain on TMJ area; more females reported pain on TMJ area (P = 0.012).
Most of the affected subjects were within the first and second age groups. Table 3 shows the prevalence of each symptom according to gender and age groups. There was no significant gender difference in the occurrence of TMD symptoms except for the symptom pain on temporomandibular joint area which occurred more among females (as shown in Table 4) When comparing the prevalence of each symptom within the different age groups, apart from clenching, the results showed no significant difference between the different age groups and all TMD symptoms (Noise, limited jaw movement, pain on TMJ area, locked jaw and pain on function). Students in the third age group had the highest prevalence (p value of 0.000) of clenching compared with the other age groups. The age-wise prevalence distribution is shown in Table 5. Regarding causative effect of TMD risk factors on the development of TMD symptoms, the results revealed that previous trauma was significantly associated with increased risk of limited joint movement (p = 0.013). Both headache and stress were statistically associated with all TMD symptoms except joint noise.
Artheralgia did significantly increase the risk of pain on temporo-mandibular joint area and clenching. Previous joint treatment was significantly associated with increased pain levels on temporo-mandibular joint area and the development of a locked jaw situation. The associations between TMD symptoms and the associated risk factors are shown in Table 6.

Discussion
Although TMD is a prevalent disease affecting young adults (Magnusson et al 2000), there is lack in the literature about its prevalence in the Palestinian population. Accordingly, the aim of this study was to study the prevalence of TMD symptoms among a group of university students.
In this study, students from the dental and medical fields were chosen to answer the questionnaire because they have more knowledge about the temporomandibular joint problems compared to students from other faculties in the university.
The results of this study revealed a high prevalence (63.5%) of TMD symptoms among the investigated students. This result was close to what was found by some other studies. [10,11] Among the investigated TMD symptoms, clenching was the most prevalent among the investigated students with a prevalence of about 35.6% (148/416 students). This result was in agreement with other studies which proved the strong relationship between clenching and the development of TMD. [12] Joint Noises were the second most reported symptom with a prevalence of about 33.4% (139/416 students).
Apart from clenching, no significant correlation between different age groups and the reported TMD symptoms (Noise, limited jaw movement, pain on TMJ area, locked jaw and pain on function). Other studies reported similar results. [13] [14] In Most of the studies, females reported higher prevalence of TMD symptoms than males. Contrary to most studies reported in the literature, in this study there was no significant gender difference in the occurrence of TMD symptoms except for the symptom pain on temporomandibular joint area which occurred more among females. [10][11][16][17][18][19][20] Students in the third age group had the highest prevalence of clenching symptom compared to other groups. This could be explained by the fact that students in the graduation years may suffer high levels of anxiety, stress and headache that may trigger the development of TMD symptoms. This goes in hand with what was found by Gerke et al. (1990) who proved the intimate relationship between psychological and emotional factors and the development of TMD. [15] This study revealed that stress and headache are closely related to the development of TMDs. Headache was the risk factor mostly associated with the TMD development followed by stress. This finding goes in part with what was found by Young (1999) who considered headache as being the most common risk factor associated with TMD development. [21][22][23]

Conclusion
Based on the findings of our study, a high prevalence of TMD among Palestinian medical students with female students reporting more pain on TMJ than males.Age group (23 to 25) years reported more frequency of clenching than the other age groups and a strong correlation was found between stress, headache and TMD.

Disclosure of conflict of interest
There is no conflict of interest exist among all authors.

Statement of informed consent
Informed consent was obtained from all individual participants included in the study.